Process integration and electrification through multiple heat pumps using a Lorenz efficiency approach

Abstract

This paper introduces a novel method for targeting the minimum shaft work required for process electrification employing principles of Pinch Analysis and detailed heat pump performance estimations. The method deviates from conventional Pinch Analysis by dividing the grand composite curve (GCC) into net heat sink and source profiles to enable the placement of heat pumps exploiting the heat pockets of the GCC. Additionally, it employs Lorenz efficiency over exergy efficiency, offering an accurate description of heat pump performance and highlighting the importance of integration between processes. The method is applied to two case studies. The first case, milk evaporator, focused on the placement of heat pumps in the heat pockets of the GCC. The results showed that while the maximum direct heat recovery was 20,447 kW, the optimal configuration limited the heat recovery to 12,199 kW, reducing the shaft work from 1,930 kW to 1,010 kW. The second, a spray dryer case, focused on the integration of electric boilers and the partial process electrification when available excess heat is limited. In this case, 1,520 kW out of 4,640 kW were covered by an electric boiler, with a biomass boiler replacing the electric boiler to cover 3,570 kW if available.